ABCDon Grady, center, played Robbie Douglas on "My Three Sons," with Stanley Livingston, left, Fred MacMurray, second from left, Barry Livingston, front, and William Demarest, right.

Former teen idol Don Grady, who played Robbie Douglas on “My Three Sons,” died Wednesday at 68 after suffering from cancer. Barry Livingston, who played Grady’s younger brother on the classic ’60s show, confirmed the death to the Associated Press.

“It’s the oldest cliché in the world when TV brothers start referring to each other like biological brothers, but he was the oldest, and somebody I looked up to and learned from a great deal about life,” Livingston says.

Grady, a former Mouseketeer, continued to act sporadically into the 1980s but his true love was music, and he wrote the theme song for “The Phil Donahue Show,” and music for “The Phanton of the Opera” star Michael Crawford’s Las Vegas show, the AP reports.

Doris Singleton, who played Lucy Ricardo’s stuck-up frenemy Carolyn Appleby on “I Love Lucy,” has died at the age of 92 in Los Angeles, Lucille Ball’s daughter Lucie Arnaz confirmed in a Facebook post, according to People.com.

“A day of saying hasta luego to two great ladies, Nora Ephron[who died Tuesday] and Doris Singleton,” Arnaz writes. “May they both fly swiftly heavenward and enjoy a blissful rest for jobs well done down here. They were loved and appreciated and will be missed.”

Singleton made 10 appearances on “I Love Lucy,” as well as Ball’s later shows, and guest-starred on a host of other shows, from “The Munsters” to “Marcus Welby, M.D.” to “Dynasty.”